I. Field of the Invention
The present invention is directed to a balloon dilatation catheter for use in the treatment of occluded arteries such as in heart disease, and more particularly, to a long balloon structure for use in tapered or bent blood vessels.
II. Prior Art
Percutaneous transluminal coronary angioplasty (PTCA) is a well known method for myocardial revascularization. The method consists of using a balloon catheter such as disclosed in U.S. Pat. No. 4,323,071 to Simpson et al to open or dilate stenoses or lesions located in blood vessels. Simpson et al disclose a catheter system having an inflatable short balloon mounted on a dilatation element support hose. The catheter system is percutaneously introduced into the body via the femoral artery. The catheter system is advanced through the vascular system over a guide wire and the balloon is positioned within the stenosis to be opened. Inflation liquid is then introduced into the interior of the balloon through the catheter system by a hand syringe to inflate the balloon. Inflation of the balloon causes a dilatation of the plaque forming the lesion. The plaque is compressed against the wall of the vessel resulting in increased blood vessel lumen size with increased blood flow.
Although PTCA has been very successful in treatment of stenoses, it has been found that the length of the lesion is an important factor in the success of PTCA. As reported by Ryan et al in "Guidelines For Percutaneous Transluminal Coronary Angioplasty: A Report Of The ACC/AHA Task Force on Assessment of Diagnostic and Therapeutic Cardiovascular Procedures" in J Am Coll Cardiol 1988; 12:527-545, lesions exceeding 2 cm in length have a low procedural success rate and a high rate of subsequent major cardiac events such as abrupt closure, death, myocardial infarction, or dissection during the procedure. In the event of severe dissection or closure, bypass surgery is usually required. Ryan et al also recorded that the success rate of PTCA is reduced significantly when lesions are located at sharp bends in the vessel. For instance, lesions located in a vessel having a bend angle of 45.degree. but less than 90.degree. have been associated with moderate success (60-85%) and complication rates. However, when the lesions are located in a bend having an angle of greater than 90.degree., the success rate decreases to less than 60% and the complication rate increases. Lesions which are both long and located on a bend represent a significantly greater risk of complication than lesions having only one of those characteristics. See Ellis et al American Journal of Cardiology, 1990, 66:932-7.
Conventional balloon catheters such as disclosed in U.S. Pat. No. 4,323,071 have dilatation balloons with an axial length of between 1 and 2 cm. In treating long lesions, the conventional balloon is subject to multiple fragmented inflations where the balloon is inflated within the stenosis at one position and then deflated and moved axially within the stenosis to an adjoining position and reinflated to dilate the stenosis.
It has been suggested that the use of dilation catheters having a balloon with a length of 3.0 to 4.0 cm may improve the outcome of PTCA in lesions having a length greater than 2 cm. See Savas et al Journal of American College of Cardiology, 19 (3:34A) 1992. It is suggested that these so called "long balloons" will more evenly distribute pressure throughout the entire length of the diseased section. The long balloon also eliminates the need for repeated multiple fragmented inflations across the diseased segment, thereby reducing the risk of tissue injury.
Long balloons have recently been produced by Advanced Cardiovascular System (ACS) of Mountainview, Calif. ACS produces long balloons having a length of either 3.0 cm or 4.0 cm and the results from the use of long balloons appear to be superior to the results from using balloons of conventional lengths. However, risks remain of subsequent major cardiac events from PTCA in long lesions, particularly in vessels which are bent at an angle greater than about 45.degree..